When it comes to portraiture, I think the most important thing is understanding how the face is made up of a lot of separate "planes". Beginners will usually try to draw the face as a sort of singular flat surface, but as one gets a better grasp of the major planes in which it can be divided, they can better understand how the face exists as a three dimensional structure.

The way Drawabox is designed isn't as a small-scale tutorial. It definitely includes things in it that will individually improve aspects of your art (mainly as individual tools, like the ghosting method, the concept of drawing from your shoulder, etc) but as a whole, it's a course that is meant to put you through a series of exercises, in a particular order, in a particular quantity, that is designed to rewire your brain as a whole. The main concept Drawabox focuses on is teaching students to understand how the things they draw on this flat piece of paper, actually exist in 3D space - how it's made up of simple forms, and how those forms relate to one another within that space. Outside of Drawabox, you don't need to push yourself to actively try to apply what you're learning - if the course works as intended, it's going to gradually sneak its way into your work by changing the way in which you see the world, and the kinds of habits with which you approach drawing as a whole. Long story short - relax. Just focus on following the instructions to the letter, including the instructions on the rotated box exercises which state that you're probably going to have a horrible time with that exercise. Try it once, and move on. There are exercises in the course that are specifically assigned at points where you're not expected to be able to pull them off especially well - it's part of the process.